You don't need an IR to be an instructor.
The most sensible route in my view is PPL-Night-CPL-FI(A)
You don't need the CPL to be an instructor, but if you're starting from scratch you won't save any money by not doing it, so you may as well.
You need to at least do CPL groundschool, but instead you could do the full ATPL groundschool. If you do this, you then have 3 years to get a CPL and IR, otherwise the groudschool expires.
So my view would be do CPL-FI(A), then in 2 years look at whether you need or want an IR and do it then. If at that point you decide you don't want the IR, all it's cost you is a few extra exams in the onset. Much better than the other way round where you suddenly decide that you want an IR and need to sit 14 exams to get it.
After two years in the industry you'll have a much better idea of whether an IR would benefit you. At this point the only reason to do it would be for an airline job.